1. The Field of the Disclosure
The present disclosure relates generally to testing and evaluation of medical devices and, in particular, to testing and evaluation of medical devices while the devices are subjected to dynamic forces.
2. The Relevant Technology
Implantable medical devices can be used to treat conditions interior to a patient, such as within a patient's vascular system. Stents are one type of implantable medical device. Stents are tubular structures generally constructed of metals such as stainless steel, CoCr, Nitinol or other alloys, as well as polymers. Stents can be constructed to be either self-expanding structures that utilize superelastic properties of the material of which they are constructed or balloon-expandable structures that are expanded through plastic deformation. Such devices can be used to treat vascular conditions.
As stenting has become increasingly applied, procedural technical success rates have increased and the superiority of stenting over simple percutaneous angioplasty has been demonstrated. However, occlusive atherosclerotic lesions (blockages) in the femoropopliteal artery can be difficult to treat endovascularly. In particular, in-stent restenosis generally remains a significant clinical problem, as study findings show restenosis in about 46% of stented patients after two years. Restenosis refers to the obstruction of the blood vessel due to the formation of scar tissue in a vessel in response to an adverse interaction between the stent and the vessel wall.
The reasons for the high rate of restenosis in stented femoropopliteal arteries have not been fully elucidated. One hypothesis is that in-stent restenosis may be a function of the unique biomechanical forces (axial extension and contraction, flexion or bending, radial compression, and torsion) present in stented leg arteries. Additionally, stent fractures have been reported, which may be one cause of restenosis. Other studies have detailed attempts to evaluate femoropopliteal motion in vivo and in cadaveric models. These studies, while valuable, are generally expensive to conduct and limited in sample size and scope. These studies have not previously been extended to physiological bench-top model evaluations where numerous samples can be evaluated without difficulty.
Further, while in vivo and cadaveric studies can be useful in providing information about the performance of a single type of medical device in a single realistic environment, it can be difficult to determine performance characteristics of the medical device compared to other medical devices. For example, it could be unduly intrusive or even harmful to introduce various medical devices into a patient for the purposes of evaluating relative performance. Even if such a procedure were undertaken, the environment differences existing within the same patient could vary enough to make useful comparison difficult.
Furthermore, studies involving humans have data varying over a spectrum that does not allow for the accurate portrayal of detecting stent deformations. Clinical and cadaveric studies have expensive procedures in purchasing cadavers, catheter lab equipment, and vendors and may require a skilled physician for handling. Moreover, those studies may be time consuming in acquiring data. Furthermore, clinical and cadaveric studies do not allow for easy observation of the inner-workings of the human leg.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.